Relax model validation when saving pages as draft

docs/reference/signals.md

@@ -113,6 +113,7 @@ def clear_page_url_from_cache_on_move(sender, **kwargs):
 pre_page_move.connect(clear_old_page_urls_from_cache)
 ```
 
+(page_slug_changed)=
 ## `page_slug_changed`
 
 This signal is emitted from a `Page` when a change to its slug is published.

docs/releases/6.5.md

@@ -54,6 +54,10 @@ depth: 1
 
 ## Upgrade considerations - changes affecting all projects
 
+### `Page.save()` no longer automatically calls `full_clean` for draft pages
+
+In previous releases, the `save()` method on page models called the `full_clean` method to apply [model-level validation rules](inv:django#validating-objects), regardless of whether the page was in a draft or live state, unless this was explicitly disabled by passing `clean=False`. As of this release, saving a page in a draft state (`live=False`) will only perform the minimum validation necessary to ensure data integrity: the title must be non-empty, and the slug must be unique within the parent page. Saving a page with `live=True` will apply full validation as before. If you have user code that creates draft pages and requires them to be validated, you must now call `full_clean` explicitly.
+
 ## Upgrade considerations - deprecation of old functionality
 
 ### `TAG_LIMIT` and `TAG_SPACES_ALLOWED` settings renamed to `WAGTAIL_TAG_LIMIT` and `WAGTAIL_TAG_SPACES_ALLOWED`

wagtail/models/pages.py

@@ -650,8 +650,7 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
         self._set_core_field_defaults()
         super().full_clean(*args, **kwargs)
 
-    def clean(self):
-        super().clean()
+    def _check_slug_is_unique(self):
         parent_page = self.get_parent()
         if not Page._slug_is_available(self.slug, parent_page, self):
             raise ValidationError(
@@ -663,6 +662,15 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
                 }
             )
 
+    def clean(self):
+        super().clean()
+        self._check_slug_is_unique()
+
+    def minimal_clean(self):
+        self._set_core_field_defaults()
+        self.title = self._meta.get_field("title").clean(self.title, self)
+        self._check_slug_is_unique()
+
     def is_site_root(self):
         """
         Returns True if this page is the root of any site.
@@ -682,25 +690,35 @@ class Page(AbstractPage, index.Indexed, ClusterableModel, metaclass=PageBase):
     # ensure that changes are only committed when we have updated all descendant URL paths, to preserve consistency
     def save(self, clean=True, user=None, log_action=False, **kwargs):
         """
-        Overrides default method behavior to make additional updates unique to pages,
-        such as updating the ``url_path`` value of descendant page to reflect changes
-        to this page's slug.
+        Writes the page to the database, performing additional housekeeping tasks to ensure data
+        integrity:
 
-        New pages should generally be saved via the :meth:`~treebeard.mp_tree.MP_Node.add_child`
-        or :meth:`~treebeard.mp_tree.MP_Node.add_sibling`
-        method of an existing page, which will correctly set the ``path`` and ``depth``
-        fields on the new page before saving it.
+        * ``locale``, ``draft_title`` and ``slug`` are set to default values if not provided, with ``slug``
+          being generated from the title with a suffix to ensure uniqueness within the parent page
+          where necessary
+        * The ``url_path`` field is set based on the ``slug`` and the parent page
+        * If the ``slug`` has changed, the ``url_path`` of this page and all descendants is updated and
+          a :ref:`page_slug_changed` signal is sent
 
-        By default, pages are validated using ``full_clean()`` before attempting to
-        save changes to the database, which helps to preserve validity when restoring
-        pages from historic revisions (which might not necessarily reflect the current
-        model state). This validation step can be bypassed by calling the method with
-        ``clean=False``.
+        New pages should be saved by passing the unsaved page instance to the
+        :meth:`~treebeard.mp_tree.MP_Node.add_child`
+        or :meth:`~treebeard.mp_tree.MP_Node.add_sibling` method of an existing page, which will correctly update
+        the fields responsible for tracking the page's location in the tree.
+
+        If ``clean=False`` is passed, the page is saved without validation. This is appropriate for updates that only
+        change metadata such as `latest_revision` while keeping content and page location unchanged.
+
+        If ``clean=True`` is passed (the default), and the page has ``live=True`` set, the page is validated using
+        :meth:`~django.db.models.Model.full_clean` before saving.
+
+        If ``clean=True`` is passed, and the page has `live=False` set, only the title and slug fields are validated.
         """
         if clean:
-            self.full_clean()
-        else:
-            self._set_core_field_defaults()
+            if self.live:
+                self.full_clean()
+            else:
+                # Saving as draft; only perform the minimal validation to satisfy data integrity
+                self.minimal_clean()
 
         slug_changed = False
         is_new = self.id is None

wagtail/tests/test_management_commands.py

@@ -349,7 +349,7 @@ class TestPublishScheduledPagesCommand(WagtailTestUtils, TestCase):
             .exists()
         )
 
-        with self.assertNumQueries(47):
+        with self.assertNumQueries(42):
             with self.captureOnCommitCallbacks(execute=True):
                 management.call_command("publish_scheduled_pages")
 

wagtail/tests/test_page_model.py

@@ -104,6 +104,19 @@ class TestValidation(TestCase):
         with self.assertRaises(ValidationError):
             homepage.add_child(instance=hello_page)
 
+    def test_title_is_required_for_draft_page(self):
+        homepage = Page.objects.get(url_path="/home/")
+
+        hello_page = SimplePage(slug="hello-world", content="hello", live=False)
+        with self.assertRaises(ValidationError):
+            homepage.add_child(instance=hello_page)
+
+        hello_page = SimplePage(
+            title="", slug="hello-world", content="hello", live=False
+        )
+        with self.assertRaises(ValidationError):
+            homepage.add_child(instance=hello_page)
+
     def test_slug_is_autogenerated(self):
         homepage = Page.objects.get(url_path="/home/")